首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2260篇
  免费   227篇
  国内免费   39篇
耳鼻咽喉   25篇
儿科学   26篇
妇产科学   253篇
基础医学   835篇
口腔科学   21篇
临床医学   94篇
内科学   299篇
皮肤病学   199篇
神经病学   19篇
特种医学   16篇
外科学   104篇
综合类   160篇
预防医学   45篇
眼科学   12篇
药学   69篇
中国医学   26篇
肿瘤学   323篇
  2024年   7篇
  2023年   54篇
  2022年   53篇
  2021年   116篇
  2020年   112篇
  2019年   103篇
  2018年   92篇
  2017年   96篇
  2016年   81篇
  2015年   88篇
  2014年   125篇
  2013年   139篇
  2012年   93篇
  2011年   109篇
  2010年   83篇
  2009年   75篇
  2008年   82篇
  2007年   82篇
  2006年   85篇
  2005年   74篇
  2004年   69篇
  2003年   79篇
  2002年   64篇
  2001年   52篇
  2000年   51篇
  1999年   42篇
  1998年   40篇
  1997年   46篇
  1996年   45篇
  1995年   39篇
  1994年   38篇
  1993年   29篇
  1992年   33篇
  1991年   24篇
  1990年   17篇
  1989年   22篇
  1988年   18篇
  1987年   18篇
  1986年   7篇
  1985年   8篇
  1984年   5篇
  1983年   10篇
  1982年   6篇
  1981年   5篇
  1980年   2篇
  1979年   1篇
  1978年   3篇
  1977年   4篇
排序方式: 共有2526条查询结果,搜索用时 15 毫秒
1.
2.
Follicular fluids from eight patients with one ovary and from ten patients with two ovaries were investigated for bioactive inhibin, total renin, oestradiol (E2) and progesterone (P4) concentrations. Four follicular fluids were pooled per patient before assessment. All women had been stimulated similarly using a protocol including a GnRH agonist, HMG and HCG. Renin levels were significantly lower and P4 significantly higher in pools of follicular fluid from patients with one ovary, whereas inhibin and E2 concentrations were similar in both patient groups. A significant negative correlation was found in the pools of follicular fluid between inhibin and E2 in both groups. These results suggest a role for inhibin and renin in the paracrine and autocrine control of stimulated follicular development.  相似文献   
3.
The determination of penetration pathways of topically applied substances into the skin is the subject of several investigations. Recently, follicular penetration has become a major focus of interest. To date, a direct, non-invasive quantification of the amount of topically applied substance penetrated into the follicles had not been possible. The development of such a method was the aim of this study. Therefore, the advantages of both stripping techniques, tape stripping and cyanoacrylate skin surface biopsy, were combined and evaluated. Tape stripping was used to remove the part of the stratum corneum that contained the topically applied dye. Subsequently, the follicular contents were ripped off by cyanoacrylate skin surface biopsy. The combined method termed "differential stripping" was evaluated in vitro and in vivo , and the amount of topically applied fluorescent dye penetrated into the hair follicles was quantified after different penetration times. After 30 min, 5% of the recovered concentration of sodium fluorescein was found in the follicular infundibula, where it was still detectable after 48 h. Altogether, the results of this investigation revealed that differential stripping is a new method that can be used to study the penetration of topically applied substances into the follicular infundibula non-invasively and selectively.  相似文献   
4.
Diversion colitis refers to the inflammatory changes that occur in the defunctioned segment of the large intesting following diversion of the faecal stream. We report the histological features in the defunctioned rectums from seven patients: one each with severe constipation and Behcet's disease, two with Crohn's disease with rectal sparing and three with ulcerative colitis. The appearances of diversion colitis in a previously normal rectum are compared with diversion colitis with superimposed inflammatory bowel disease. Lymphoid follicular hyperplasia was found in all cases. This was marked in patients with inflammatory bowel disease. with or without initial rectal involvement. Other changes comprised surface epithelial degeneration and ulceration, mucosal inflammation including crypt abscesses, and crypt branching. Inflammatory and crypt changes were mild, except in ulcerative colitis where changes were marked and resembled those of the proximal colon. Lymphoid hyperplasia is a distinctive feature in diversion colitis. The term follicular proctitis, previously used to indicate chronic ulcerative colitis exclusively, should be re-examined.  相似文献   
5.
6.
人卵泡液中干细胞因子水平及其对卵泡发育的影响   总被引:3,自引:1,他引:2  
目的 :探讨人卵泡液中是否存在干细胞因子 (SCF)及其与卵泡发育的关系 .方法 :采用夹心ELISA方法检测 3 0例进行体外受精 胚胎移植 (IVF ET)患者超促排卵前、取卵时血清与卵泡液中SCF的水平 .结果 :①取卵时卵泡液中SCF水平 (5 14± 67)ng·L 1,显著高于同期血清水平 (3 95± 4 9)ng·L 1,差别有显著性 (P <0 .0 5 ) ;②取卵时血清中SCF水平与超促排卵前血清中SCF水平相比 ,差别无显著性 [(3 95± 4 9)ng·L 1,(3 74± 3 6)ng·L 1,P >0 .0 5 ];③高、中反应型组卵泡中SCF水平 [(5 64± 64)ng·L 1,(5 3 2± 5 5 )ng·L 1]与低反应型 (3 5 2± 78)ng·L 1相比 ,差别有显著性 (P <0 .0 1) ,且与卵泡发育数目之间呈正相关 (r =0 .4 12 ,P <0 .0 5 ) .结论 :卵泡液中SCF可能来自于卵泡本身 ,而非血浆渗透 .SCF参与人卵泡发育的调控  相似文献   
7.
OBJECTIVE: To evaluate the follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels in early follicular phase throughout the reproductive years. METHOD: FSH and LH concentrations were determined by radioimmunoassay (RIA). Linear and polynomial regressions were carried out considering basal FSH as the dependent and age as the independent variable. RESULTS: FSH levels increased throughout the reproductive years (P<0.025). A positive correlation between age and basal FSH levels was detected (P<0.05). The Pearson squared coefficient of r(2)=0.889 was obtained. Using polynomial regression, the inclination of the parabole (Y=7.97-0.009x+0.057x(2)) was 0.359 and the generalized correlation coefficient was r=0.795. The goodness of fit analysis showed that the parabole may better represent the phenomenon (F=4.7; P<0.05). The LH levels remained constant, increasing only beyond 40 years of age. CONCLUSION: The FSH levels rose in a nonlinear way during the reproductive life and the LH concentrations increased discreetly only in patients over 40 years of age.  相似文献   
8.
Mice rendered deficient for interleukin (IL) 6 by gene targeting were evaluated for their response to T cell–dependent antigens. Antigen-specific immunoglobulin (Ig)M levels were unaffected whereas all IgG isotypes showed varying degrees of alteration. Germinal center reactions occurred but remained physically smaller in comparison to those in the wild-type mice. This concurred with the observations that molecules involved in initial signaling events leading to germinal center formation were not altered (e.g., B7.2, CD40 and tumor necrosis factor R1). T cell priming was not impaired nor was a gross imbalance of T helper cell (Th) 1 versus Th2 cytokines observed. However, B7.1 molecules, absent from wild-type counterparts, were detected on germinal center B cells isolated from the deficient mice suggesting a modification of costimulatory signaling. A second alteration involved impaired de novo synthesis of C3 both in serum and germinal center cells from IL-6–deficient mice. Indeed, C3 provided an essential stimulatory signal for wild-type germinal center cells as both monoclonal antibodies that interrupted C3-CD21 interactions and sheep anti–mouse C3 antibodies caused a significant decrease in antigen-specific antibody production. In addition, germinal center cells isolated from C3–deficient mice produced a similar defect in isotype production. Low density cells with dendritic morphology were the local source of IL-6 and not the germinal center lymphocytes. Adding IL-6 in vitro to IL-6–deficient germinal center cells stimulated cell cycle progression and increased levels of antibody production. These findings reveal that the germinal center produces and uses molecules of the innate immune system, evolutionarily pirating them in order to optimally generate high affinity antibody responses.  相似文献   
9.
A 58-year-old Japanese woman who had herpes zoster in association with colitis was successfully treated with intravenously administrated acyclovir. Vesicular lesions with red haloes ranged from the left side of her buttock to the left extremity, corresponding to the L4 to S2 dermatomes. Her colitis was considered to have been induced by varicella-zoster virus, based on the facts that the clinical courses were correlated and that the innervation of the affected site of the colon corresponded to an infected dermatome (S2).  相似文献   
10.
不同强度运动对女子游泳运动员性激素水平的影响及特点   总被引:7,自引:0,他引:7  
本研究以放兔分析法观察不同强度运动前后19名女子游泳运动员血清促卵泡激素(FSH)、黄体生成素(LH)、雌二醇(E_2)、孕酮(P)、睾酮(T)及胰岛素(Ins)的变化。受试者在卵泡及黄体两期分别进行短时间高强度间歇运动——6×50m全速力竭性游泳和长时间持续运动——1000m全速力竭性游泳。在运动前5分钟及运动后即刻分别采集静脉血测定各种激素含量。主要结果如下:受试者从事6×50m最大速度间歇游泳后,卵泡期各种激素浓度的变化均显著高于运动前安静状态,黄体期变化不一,FSH、LH降低,E_2、P、T及Ins升高。从事1000m全速游泳后,激素变化表现为卵泡期FSH、LH、E_2、P均升高,T及Ins降低;黄体期E_2、P、T升高,Ins降低,FSH、LH无显著变化,两期相比黄体期运动成绩优于卵泡期。上述结果提示:①受试者月经周期的黄体期机体有氧能力强于卵泡期,运动能力的增强与黄体期E_2、P、T水平升高有关。②FSH、LH与E_2、P分泌变化并非同步一致,说明运动中E_2升高并非受制于促性腺激素,而主要是卵巢分泌量升高所致。③运动中E_2、P、T具有协同效应,可抵抗疲劳,提高人体运动能力。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号